Comfy boots are important. Nowadays I'd focus on something GoreTex lined (it's a wet country) and not leather. No need to go to £100 as long as they are a good fit. Go to a proper walking shop to get them fitted and be prepared to walk around a lot indoors (up and down steps if you can) to make sure they fit well before wearing them outside.
Poles might be a good idea if you are carrying any leg injuries. Other than full-on winter walking, or backpacking, I hardly use mine.
Layering up with your clothing works, using whatever you have. However, I'd avoid natural materials as they tend to soak up sweat. A good baselayer an insulating layer and a waterproof layer still works well as a concept. If your snowboarding jacket is both insulating AND waterproof you may find it a bit warm when it's not raining.
Avoid wearing jeans or any heavy cotton on your legs. Unless it's absolutely chucking it, or very cold, I tend just to suffer damp legs.
Gaiters avoid the creep of mud and wet up your trousers and are well worth it outside of summer.
Warm gloves can be a life-saver.
For this time of year, a decent sized rucksack will let you take some spare clothing, a map and compass (make sure you know how to use them), torch, whistle, a flask and some food and drink.
Most of all, just relax and enjoy it. You live beside some beautiful countryside and you are at a good time of the year to see it changing through the seasons.